Elevator buffer



E. E. ARNOLD ELEVATOR BUFFER Aug. 23, 1932.

Filed Sept. 18. 1929 Fig.2.

Fig.1.

INVENTOR Edwin E. flrnoid.

ATTORNEY Patented Aug. .23, 1932 UNITED STATES PATENT OFFICE 23 EDWIN E.ARNOLD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC &MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA ELEVATOR BUFFERApplication filed September 18, 1929. Serial No. 393,438.-

' ern elevator is toward increased speed of operation. For example, 500to 600 feet per minute has been considered the maximum elevator speedconsistent with comfort and safety. Recent developments in electricalcontrol have demonstrated the practicability of the use of car speeds of900 or more feet per minute.

However, when such high speeds are employ'ed, a new problem is presentedto the elevator engineer in designing buffers and safety stops forinsuring the gentle stopping of the car at the top and the bottom of theelevator shaft, in the event that the electrical control of the carfails.

While safety buffers have long been used for this purpose, they have allbeen designed with short strokes accommodated to the lower speedsofoperation of the cars, and hence,

these old buffers are inadequate to safely stop the cars from the higherspeeds, since the stored'energy to bearrested and absorbed by the buflerincreases as the square of the speed.

The solution appears to be either the use of a greater force actingthrough the distance of the short stroke or the use of alesser forceacting through a much longer stroke. T'o exert a greater force wouldresult in the too rapid checking of the speed of the car, therebyendangering the passengers, as well as the p enclosed within a chamberwhich surrounds the stationary rod. The fluid provides a' equipment; A

However, to increase the length of I the stroke of the buffer presentsthe problem of retrieving the buffer to its extended position after itsoperation. The use of springs for this purposejis limited tocomparatively short-stroke buffers because of the relatively shortexpansion characteristic of springs, and the use of combinations ofsprings is not satisfactory because such combinations are unwieldy andcumbersome.

An object of my invention, therefore, is to provide a buffer forelevators having a long stroke and one which does not require the use ofa long spring to retrieve it after it has been operated.

Another object of my invention is to provide a bufler, the moving partsof which have a minimum weight, thereby reducingshocks due to inertia ofsuch parts when getting them under way at the high speed of initialcontacts of the mass to be brought to rest.

Another object is to employ, in such buffers, a dense fluid mediumadapted to give a higher dynamic resistance than oil so that smallerpressure areas may be employed.

Another object is to eliminate the use of long springs as a restoringmeans to which My inventioncomprises essentially a rela-' tively longhollow buffer ram slidably mounted upon, and telescopically engaging, arelatively stationary rod or plunger. Means are provided to entrap airwithin the hollow ram above the plunger which is compressed during anoperating stroke and expanded to retrieve the ram.

A mass of mercury or like dense fluid is force resistant to theoperating stroke of the ram 4 and is bypassed along the ram toward itsfree end. i

A combination is thereby provided wherein two fluids are effective toyieldingly resist the motion of the buffer ram, upon an application offorce thereto, and retrieve the ram to its original position uponremoval of the applied force.

My invention also embodies a novel auxiliary buffer associated with themain butler,

and in series therewith, for absorbing ini- Parts having the samefunctions will be designated by the same reference character in bothfigures.

In Fig. 1 is shown an outer casing 1 within which is disposed a cylinder2 which contains a resistance fluid 3 of high density, preferablymercury. A hollowram 4, which is the principal shock-absorbing element,has a cap l on its upper end, its lower end being fitted to 4reciprocate in cylinder 2.

An opposing plunger 5 extends substantially the full length of thecylinder 2 and 1s centrally disposed within the latter to form a chambertherebetween and is fitted to slide within the ram 4. Plunger 5 andcylinder 2 are'held in fixed relation by being attached to a common base6 comprising a piston in the cylindricalcasing 1.

A fluid seal is maintained between the ram 4 and the plunger 5 by meansof a sealing ring 7, disposed adjacent to the upper end of the plunger5, together with a small amount of mercury 7 placed above its ring. Bymeans of this seal, air is entrapped within the ram 4, thereby forming acushion below it. The chamber between the cylinder 2 and the plunger 5is filled with mercury or like dense fluid. .Vhen mercury is employed asthe resistant fluid, it will have considerable buoyant effect on the raml which, as will be seen, is always partially immersed therein. With thebuoyancy of the mercury assisting the air cushion in supporting the raml, only a slight air pressure is necessary to maintain it in an extendedposition. As will be explained below, the mercury and entrapped airoperates on the associated elements to retrieve the ram 4 after it hasbeen. forced into its retaining cylinder 2. It is apparent that thepressure of the air forming said cushion may be suflicient to retrieveand support the ram 4.

When the ram 4 is forced downwardly, its movement is resisted by themercury, or other fluid, in cylinder 2 which is displaced and escapesthrough an annular space between the outer wall of the ram and the innerwall of the cylinder, and into overflow chamber 8. This space isprovided by fitting the ram l into the cylinder 2 with the proper amountof clearance. By making the clearance greater or less, any desiredresistance may be secured.

The same clearance is maintained between ram 4 and cylinder 2 throughouttheir entire lengths. As the ram is forced down into the cylinder, theabove mentioned annular space is lengthened. Owing to the high surfacetension of mercury and the increase in length of the space through whichit must flow, its resistance to flow is correspondingly increased. 1thereby obtain the desired characteristic of increased resistance of theshockabsorbing element as it approaches its limit of travel.

It is desirable, in heavy duty high-speed buffers of this type, toabsorb the initial shock of impact of the applied force, by utilizingthe combined shock-absorbing effect of two bufl'ers operating in seriesat the instant of impact and for a limited portion of the stroke. This Iaccomplish by using a long-stroke fluid-resistance buffer comprising asolid plunger and a short-stroke auxiliary bulier with a springretrieving means associated therewith. This provides a sufficientlyeffective arrangement wherein a relatively large amount of fluid isdisplaced.

Such an auxiliary buffer may comprise an auxiliary buifer chamber 9 atthe bottom of the casing 1, as shown in Fig. 1, and this chamber isfilled with oil or like fluid. Base,

operates, through cylinder 2, to retrieve base- 6 and the parts movingin unison therewith.

Base 6 is depressed by the force exerted upon ram 4, which force istransmitted to the piston 6 through the fluid in cylinder 2 and the airabove ram 5, whereupon piston 6 is. moved downwardly upon the oil 1nchamberv 9 and, at the same time, compresses spring 10 in the chamber11. The downward movement of the piston 6 in chamber 9 is resisted bythe oil in the chamber as it flows around the piston passing from belowto above it as it descends. Upon removal of the applied force, spring.10 acts against the base of chamber 8 to force piston 6 and itsassociated parts upwardly, and the displaced oil will be returned fromcasing 11 into chamber 9, thereby restoring the base 6 to its originalposition.

Fig. 2 shows another form of my inven tion wherein the auxiliary bufieris attached to the upper or free end of ram 4. This modification alsoincludes a series buiier action, as is embodied in Fig. 1, except thatthe applied force is first exerted on the auxweight.

ilia'r-y bufii'er instead of on the main buffer.

The adding of inertia to ram 4, bythis con-l struction, is large-1ycompensated because the initial shock is absorbed mainly by theauraliary buffer, very little of it being transmitted.

tion,to' correspondingelements in Fig. 1.

Casing 1, cylinder 2, and ram 5 are concentricallymounted on base 6which, in this embodiment, does notreciprocate as a piston butisintegral with the pedestal of the buffer. Ram 4' reciprocates incylinder 2 and functions in the same manner as in the structure shown inFig. 1. I provide a fluid seal-7 adjacent to the upper end of ram 5 toentrap air within ram4. This air, aided by the resistance .fiuid,operates to, retrieve ram 4 in the same manner as in Fig. 1. Overflowchamber 8 receives the displaced fluid from cylinder 2.

In Fig. 2, the auxiliary bulfer is located on: the'free end of ram 4. Anoil. reservoir 9 'is formed within the upper portion of ram 4, by apartition 12, within. which an auxiliary plunger 13 is slidably mountedin concentric spaced relation thereto. A spring 10 is provided tosupport the auxiliary plungerv 13 and retrieve the latter after adownward stroke thereof. A chamber 11, in communication with the openend of chamber- 9, serves as an overfiow reservoir and. also provides abase for seating spring 10, the upper end of which bears against ashoul- 1 fer-elements are concerned, but their cooperader'14 onauxiliaryplunger 13.

Either embodiment of my invention, when used in connection withelevators, is placed inthe well of the elevator shaft at the end oftravel of the elevator car or the counter- The object is to check themovement of the car or the like before it comes against the bottom ofthe elevator shaft. The car, proceeding downwardly in the shaft at a substantial rate of speed, strikes the buffer cap 4 with high initialshock, causing the ram 4'to suddenly start moving downwardly.

My-device provides for initial rapid move ment of the ram 4 through theuse of buffers ;in series with low initial fluid resistance whichincreases rapidly toward the end of the stroke, as hereinbeforedescribed.

1 In the operation of the embodiment shown in Fig. 1 the force of thedownwardly moving body is transmitted, through ram 4, to the cylinderassembly 2 and thence to piston 6. Under the action of the appliedforcc,.re sistancefluid 3'will begin to yield and bypass around ram 4 tochamber 8. At the-same time, the fluid in chamber 9 will begin to yieldand pass around piston 6 through the annular clearance space, shown inFig. 1, thereby allowing piston 6 and ram 4 to move simultaneously. I Vj For the first portion of the stroke, and

until piston 6 reaches'the bottom of chamber 9, the action of the twovbuffers will be in series, which will-allowa comparatively rapidmovement of ram 4. By the time the auxiliary bufl'er has completed itsstroke-,the initial impact shock will have been absorbed, and theinertia of the falling body. will havebeen somewhat checked. -Thecomplete retarda-- tion of thecar will be accomplished by the action oftheresistance'fluid 3 alone asthe rain 4 is forced fartherinto cylinder2. Owing to the increased resistance of the fluid, as the ram .4 movesdownwardly in cylinder 2,- the inertia of the falling car will berapidly absorbed, and the car brought to rest-without shock.

Duringv the downward movement of .ram 4, air, entrapped therein by.the'seal'7' on the upper end of ram 4, is compressed. At the sametime,thedepth of the immersion of the ram inthe fluid 3 .is increased,and spring-1O is compressed.

lVhen the car is lifted from the bufferyth-e ram 4 will be retrievedtoits original position by the action of the compressed air with in it,aided by the buoyant effect of the resistance fluid 3 upon it. Thespring 10 will operate to force the piston Gland elements assembledtherewith upwardly to their original position, thereby completelyrestoring the bufl'er'to its original condition.

The operation of the modified structure shown in Fig. 2, in which theauxiliary but fer is placed free at'the end of ram 4,. is similar, sofar as the action of the main bufauxiliary plunger to the overflowchamber 11.

The flow of the liquid around the auxiliary plunger 13 at a high rate ofspeed affords considerable'resistance which reacts downwardly on theram4 and the latter is accelerated.

By the time the auxiliary plunger 13 is'completely depressed, the ram 4has been accelerated to move at a speed substantially equal to that ofthe car. Since the hollow ram 4 was not instantly accelerated to thespeed of the car by direct engagement therewith, but was graduallyaccelerated to the speed'of the car during the stroke of the auxiliaryplunger After the car is lifted from the bufler, the buoyancy of theresistance fluid 3 and the action of the compressed air entrapped in thehollow ram 4 restores the latter to its nor- 5 mal elevated position.'The spring and the liquid associated with plunger 13 also restores itto its normal position and the device is reset for another operation.

While I have described my invention as applied to elevators, it isobvious that it may 2 in said cylinder operative to bypass the ram andproduce a buffer action with respect to the movement of said ram, withmeans associated with said ram to form an air chamber, and meanstocompress the air in said chamber during an operative. stroke of saidram, whereby the air, when compressed, is eflec tive to retrieve saidram.

2. In a fluid-resistance buffer, the combination of a cylinder, a hollowram disposed gfftO reciprocate within said cylinder, and a fluid of highdensity within said cylinder, said fluid being displaced upon a movementof said ram to yieldingly retard the motion thereof, with means for.entraining air with-' 35; in said ram, and means associated with saidram for compressing said air during an operative stroke of said ram,whereby the air,-

when compressed, is effective to retrieve said ram.

3. A buffer comprising a cylinder containing a fluid, an overflowchamber at the upper end thereof, a plunger centrally disposed withinsaid cylinder and held in a fixed relation thereto, a hollow ramarranged to slide .over said plunger and other fluid means compressiblebetween said. plunger and ram for yieldably holding said hollow ram in araised position.

buffer comprising a cylinder-con- 'itaining a fluid, an overflow chamberat the upper end thereof, a hollow ram slidable within said cylinder, anopposing. plunger slidable in said hollow ram, said cylinder and saidopposing plunger having a common base,

and means tending to hold said hollow ram in a raised positioncomprising air entrapped within said hollow ram by said opposingplunger;

5. A buffer comprising a cylinder con- .ta-ining mercury, an overflowchamber at the upper end thereof, a rod centrally disposed within saidcylinder, a base common to said cylinder and said rod, a hollow ramslidable within said cylinder and over said rod,

whereby the buoyancy ofsaid mercury acts upon said hollow ram tomaintain the latter in a raised position.

6. A fluid-resistance buffer comprising a cylinder containing a fluid, ahollow ram normally held in an extended position and slidable withinsaid cylinder in contact with said fluid, an opposing plunger disposedto slide withinsaid hollow ram and an air cushion between said ram andplunger, said air cushion and the buoyancy of said fluid being effectiveto restore said hollow ram to its extended position after displacementthereof.

7. In a buffer, an outer casing, a rod centrally disposed within saidcasing, a hollow cylinder intermediate said casing and said rod andspaced from the latter, a fluid within said space, a hollow ram slidableover said rod to engage and displace said fluid and an air cushionwithin said hollow ram above said rod.

' 8. In a buffer, an outer casing, a rod centrally disposed within saidcasing, a hollow cylinder intermediate said casing and said rod andspaced from the latter, mercury within said space and a hollow ramslidable over said rod to engage and displace said mercury, whereby thebuoyancy of said mercury tends to maintain said ram in its raisedposition.

9. A buffer comprising a cylinder, a plunger centrally disposed withinsaid cylinder and 'Xed with respect to the same to form an annular spacebetween them, a hollow ram slidable within said annular space, mercurywithin said space tending to float said hollow ram and acting as aresistance fluid during the downward stroke of said ram, an air spacewithin said hollow ram and above said mercury and sealing means carriedby said centrally disposed ram and interposed between said air space andsaid mercury to entrain air within said space, whereby the compressionof said air between the plunger and the ram acts to return the saidhollow ram toits raised position.

10. In a buffer, an outer casing, a rod centrally disposed within saidcasing, a cylinder intermediate said casing and said rod and spaced fromthe latter, a fluid within said space, a hollow ram slidable over saidrod to engage and displace said fluid, and an air cushion within thehollow ram above said rod, said cylinder and said rod being mounted on acommon base to form a unit slidable within said casin and an auxiliaryfluid reservoir within said casing and below said base.

11. In a buffer, an outer casing, a rod centrally disposed within saidcasing, a cylinder intermediate said casing and said rod and spaced fromthe latter, a fluid within said space, a hollow ram slidable over saidrod to engage and displace said fluid, an air cushion within the hollowram above saidrod and an auxiliary buffer mounted on said hollow ram.

up the initial shock upon sudden actuation thereof.

In testimony whereof, I have hereunto subscribed my name this 4th day ofSeptember,

EDWIN E. ARNOLD.

